Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A control system includes an engine control module and a transmission
control module. The transmission control module communicates with the
engine control module via a network. The engine control module generates
a mean engine speed signal and a minimum engine speed signal. The engine
control module transmits the mean engine speed signal and the minimum
engine speed signal to the transmission control module via the network.
The transmission control module controls operation of at least one of a
torque converter and a transmission based on the mean engine speed signal
and the minimum engine speed signal. The torque converter is connected
between an engine and the transmission.

Claims:

1. A control system comprising: an engine control module; and a
transmission control module that communicates with the engine control
module via a network, wherein: the engine control module generates a mean
engine speed signal and a minimum engine speed signal; the engine control
module transmits the mean engine speed signal and the minimum engine
speed signal to the transmission control module via the network; the
transmission control module controls operation of at least one of a
torque converter and a transmission based on the mean engine speed signal
and the minimum engine speed signal; and the torque converter is
connected between an engine and the transmission.

2. The control system of claim 1, wherein: the engine control module
receives at least one of an engine position signal and an engine speed
signal from an engine speed sensor; the engine control module determines
the mean engine speed based on at least one of the engine position signal
and the engine speed signal; and the at least one of the engine position
signal and the engine speed signal is indicative of an average engine
speed for at least one combustion cycle of the engine.

3. The control system of claim 1, wherein: the engine control module
determines the minimum engine speed based on a minimum of at least one of
the engine position signal and the engine speed signal; and the minimum
of the at least one of the engine position signal and the engine speed
signal is determined over a predetermined period.

4. The control system of claim 3, wherein the predetermined period
corresponds to length of a combustion cycle of the engine.

5. The control system of claim 3, wherein the predetermined period
corresponds to length of a plurality of combustion cycles of the engine.

6. The control system of claim 1, wherein the transmission control module
controls operation of the torque converter based on the mean engine speed
signal and the minimum engine speed signal.

7. The control system of claim 1, wherein: the engine control module
generates the mean engine speed signal and the minimum engine speed
signal; the engine control module transmits the mean engine speed signal
and the minimum engine speed signal to the transmission control module
via the network; and the transmission control module controls operation
of the torque converter based on the mean engine speed signal and the
minimum engine speed signal.

8. The control system of claim 1, wherein the transmission control module
adjusts slip of the torque converter based on the mean engine speed
signal and the minimum engine speed signal.

9. The control system of claim 1, wherein the minimum engine speed signal
is an offset signal that is indicative of a maximum difference between
the mean engine speed signal and a minimum engine speed of a raw engine
speed signal.

10. The control system of claim 1, wherein the minimum engine speed
signal is an offset signal that is indicative of a maximum difference
between the mean engine speed signal and a minimum engine speed of a
signal conditioned raw engine speed signal.

11. The control system of claim 1, wherein: the engine control module
generates the mean engine speed signal; the engine control module
transmits the mean engine speed signal to the transmission control module
via the network; the transmission control module determines torque of the
torque converter based on the mean engine speed signal; and controls
operation of the transmission based on the torque of the torque
converter.

12. An engine control module, comprising: a mean engine speed module that
generates a mean engine speed signal based on a raw engine speed signal;
a minimum engine speed module that generates a minimum engine speed
signal based on the raw engine speed signal; and a transceiver that
transmits the mean engine speed signal and the minimum engine speed
signal to a transmission control module via a network between the engine
control module and the transmission control module.

13. The engine control module of claim 12, wherein the transceiver
receives at least one of an engine position signal and an engine speed
signal from an engine speed sensor; the minimum engine speed module
determines the mean engine speed based on at least one of the engine
position signal and the engine speed signal; and the at least one of the
engine position signal and the engine speed signal is indicative of an
average engine speed for a plurality of combustion cycles of the engine.

14. The engine control module of claim 12, wherein the engine control
module determines the minimum engine speed based on a minimum of at least
one of the engine position signal and the engine speed signal; the
minimum of the at least one of the engine position signal and the engine
speed signal is determined over a predetermined period; and the
predetermined period corresponds to length of a plurality of combustion
cycles of the engine.

15. A control system comprising: the engine control module of claim 13;
and the transmission control module, wherein the transmission control
module control operation of at least one of a torque converter and a
transmission based on the mean engine speed signal and the minimum engine
speed signal.

16. A transmission control module comprising: a transceiver that receives
a mean engine speed signal and a minimum engine speed signal from an
engine control module via a network between the transmission control
module and the engine control module; and a torque slip module that
adjusts a torque slip of a torque converter based on the mean engine
speed signal and the minimum engine speed signal.

17. The transmission control module of claim 16, wherein the torque slip
module maintains a minimum torque slip on the torque converter based on
the mean engine speed signal and the minimum engine speed signal.

18. The transmission control module of claim 17, wherein the minimum
torque slip is set based on at least one of a predetermined number of
torque converter lock-ups and a predetermined torque converter lock-up
period.

19. The transmission control module of claim 16, further comprising: a
torque converter module that determines a torque of the torque converter
based on the mean engine speed; and a propulsion torque module that
determines a propulsion torque of the engine based on the torque of the
torque converter.

Description:

FIELD

[0001] The present disclosure relates to engine and transmission control
systems that include an engine control module and a transmission control
module.

BACKGROUND

[0002] The background description provided herein is for the purpose of
generally presenting the context of the disclosure. Work of the presently
named inventors, to the extent it is described in this background
section, as well as aspects of the description that may not otherwise
qualify as prior art at the time of filing, are neither expressly nor
impliedly admitted as prior art against the present disclosure.

[0003] An automatic powertrain system may include an engine, a torque
converter and a transmission. The torque converter includes an engine
side, a transmission side, and an electronically controlled capacity
clutch (ECCC). The torque converter converts engine output torque into
transmission input torque. A transmission control module is typically
used to maintain a target slip on the ECCC.

[0004] The smaller the target slip, the less slip in the torque converter
clutch. Decreasing slip improves transfer of energy between the engine
side and the transmission side, which improves fuel economy. However, the
smaller the target slip, the greater the chance that the torque converter
clutch will lock-up ("crash"). Control over torque transfer to the
transmission using the ECCC is lost when the torque converter clutch
locks-up, since the engine side is no longer isolated from the
transmission side of the torque converter. The amount of torque transfer
is directly related to pressure applied to the ECCC. As a result,
transmission torque can fluctuate due to changes in engine torque.
Changes in engine torque may include fluctuations due to, for example,
changes in combustion cycle speeds.

[0005] Also, the larger the target slip, the more slip in the torque
converter clutch. Increasing slip increases heat production in the torque
converter and decreases fuel economy. Excessive slip can damage the
torque converter clutch. Thus, a predetermined target slip is maintained
using the ECCC to: provide torque transfer control; minimize heat
generation in the torque converter; and satisfy fuel economy
requirements.

SUMMARY

[0006] A control system is provided that includes an engine control module
and a transmission control module. The transmission control module
communicates with the engine control module via a network. The engine
control module generates a mean engine speed signal and a minimum engine
speed signal. The engine control module transmits the mean engine speed
signal and the minimum engine speed signal to the transmission control
module via the network. The transmission control module controls
operation of at least one of a torque converter and a transmission based
on the mean engine speed signal and the minimum engine speed signal. The
torque converter is connected between an engine and the transmission.

[0007] In other features, an engine control module is provided and
includes a mean engine speed module that generates a mean engine speed
signal based on a raw engine speed signal. A minimum engine speed module
generates a minimum engine speed signal based on the raw engine speed
signal. A transceiver transmits the mean engine speed signal and the
minimum engine speed signal to a transmission control module via a
network.

[0008] In yet other features, a transmission control module is provided
and includes a transceiver that receives a mean engine speed signal and a
minimum engine speed signal from an engine control module via a network.
A torque slip module adjusts a torque slip of a torque converter based on
the mean engine speed signal and the minimum engine speed signal.

[0009] In still other features, the systems and methods described above
are implemented by a computer program executed by one or more processors.
The computer program can reside on a tangible computer readable medium
such as but not limited to memory, nonvolatile data storage, and/or other
suitable tangible storage mediums.

[0010] Further areas of applicability of the present disclosure will
become apparent from the detailed description provided hereinafter. It
should be understood that the detailed description and specific examples
are intended for purposes of illustration only and are not intended to
limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will become more fully understood from the
detailed description and the accompanying drawings, wherein:

[0012]FIG. 1 is a functional block diagram of a hybrid powertrain system
incorporating engine and transmission control in accordance with an
embodiment of the present disclosure;

[0013] FIG. 2 is a functional block and schematic diagram of a portion of
the hybrid powertrain system of FIG. 1;

[0014]FIG. 3 is a functional block diagram of an engine control module
and a transmission control module in accordance with an embodiment of the
present disclosure; and

[0015] FIG. 4 is a flow diagram illustrating a method of operating a
powertrain control system in accordance with an embodiment of the present
disclosure.

DETAILED DESCRIPTION

[0016] The following description is merely exemplary in nature and is in
no way intended to limit the disclosure, its application, or uses. For
purposes of clarity, the same reference numbers will be used in the
drawings to identify similar elements. As used herein, the phrase at
least one of A, B, and C should be construed to mean a logical (A or B or
C), using a non-exclusive logical or. It should be understood that steps
within a method may be executed in different order without altering the
principles of the present disclosure.

[0017] As used herein, the term module refers to an Application Specific
Integrated Circuit (ASIC), an electronic circuit, a processor (shared,
dedicated, or group) and memory that execute one or more software or
firmware programs, a combinational logic circuit, and/or other suitable
components that provide the described functionality.

[0018] Also, as used herein, the term combustion cycle refers to the
reoccurring stages of an engine combustion process. For example, in a
4-stroke internal combustion engine, a single combustion cycle may refer
to and include an intake stroke, a compression stroke, a power stroke and
an exhaust stroke of a cylinder. The four-strokes are repeated during
operation of the engine.

[0019] In addition, although the following embodiments are described
primarily with respect to example internal combustion engines, the
embodiments of the present disclosure may apply to other internal
combustion engines. For example, the present invention may apply to
compression ignition, spark ignition, homogenous spark ignition,
homogeneous charge compression ignition, stratified spark ignition,
diesel, and spark assisted compression ignition engines.

[0020] A target slip may be set by a calibrator and based on an operating
point of a powertrain. The target slip may be set, for example, based on
noise and/or vibration of the powertrain. This may not account for
variations in cylinder output torque or cylinder imbalance that can occur
with respect to a single engine, between multiple engines, and/or between
multiple vehicles. During a typical combustion cycle of a cylinder, which
may be operating at a steady mean speed, an engine crankshaft exhibits
fluctuations in speed due to combustion and inertial torques. Speed data
of the crankshaft includes harmonics associated with the firing frequency
of each cylinder of the engine and sub-harmonic content due to
cylinder-to-cylinder variations (i.e. cylinder imbalance).

[0021] Cylinder imbalance may be due to differences in fuel quantities,
intake air volumes, spark timing, combustion chamber volumes, valve sizes
and operation, etc. Cylinder imbalance can cause fluctuations in engine
speed. The fluctuations may be based on a firing event of each cylinder
of an engine or averaged over multiple firing events (e.g., a full
combustion cycle--2 rotations of a crankshaft).

[0022] Various torque converter and transmission control algorithms rely
on timely estimation of engine speed, acceleration, and torque. As an
example, an algorithm of a transmission control module (TCM) may adjust a
target slip or slip torque based on engine speed information. The TCM may
adjust the slip torque to account for cylinder imbalance. The engine
speed information may be provided from an engine control module (ECM) to
the TCM to account for the cylinder imbalance.

[0023] High-spatial-resolution (i.e. high-speed) measurements of an engine
may be taken detect the speed dynamics of a crankshaft. High-resolution
(raw or instantaneous) speed data may be collected by the ECM.
Transmitting instantaneous engine speed data from the ECM to the TCM
over, for example, a car area network (CAN) is generally not feasible due
to transfer speed and bandwidth capabilities of the CAN and/or processing
capabilities of the ECM and/or TCM. Further to transfer and account for
the entire instantaneous engine speed data is not needed, as pressure of
a torque converter clutch or slip torque typically can not be adjusted as
quickly as engine speed can fluctuate.

[0024] In the following described embodiments, certain engine speed
information is provided from an ECM to a TCM to allow the TCM to account
for cylinder imbalance. The engine speed information allows the TCM to
account for maximum increases and/or decreases in engine speed. The
information is transferred with minimal use in bandwidth while providing
improved torque converter and transmission system performance.

[0025] In FIG. 1, an exemplary hybrid powertrain system 10 is shown.
Although the powertrain system 10 is illustrated as a hybrid and rear
wheel drive (RWD) powertrain, it is appreciated that the embodiments of
the present disclosure can be implemented with any other hybrid and
non-hybrid powertrain configurations.

[0026] The powertrain system 10 includes a propulsion system 12 and a
drivetrain system 14. The propulsion system 12 includes an internal
combustion engine (ICE) 16 and an electric motor (EM) or a motor
generator unit (MGU) 18. The drive train system 14 includes a flexplate
or flywheel 27, a torque converter or other coupling device 30, a
transmission 32, a driveshaft 34, a differential 36, axle shafts 38,
brakes 40 and driven wheels 42. The propulsion system 12 has an ECM 50
and may have a hybrid control module (HCM) 52. The drivetrain system 14
has a TCM 54.

[0027] The control modules 50, 52, 54 share information with each other
over a network 56, such as a CAN. The ECM 50 may determine, for example,
an average or mean engine speed SEmean and a minimum engine speed
SEmin. The TCM 54 receives the mean and minimum engine speeds
SEmean, SEmin and may determine slip torque Tslip, torque
converter torque TCT, etc. The TCM 54 may also determine propulsion
torque or back torque TPROPTCM. The back torque TPROPTCM is
equal to the torque applied on the crankshaft 66 by the torque converter
30. The back torque TPROPTCM may be equal in magnitude to the output
torque of the engine 16. Thus, the engine output torque may be estimated
based on the back torque TPROPTCM. The slip torque Tslip,
torque converter torque TCT, and back torque TPROPTCM may be
based on the mean and minimum engine speeds SEmean, SEmin
determined by the ECM 50.

[0028] The ECM 50 may be able to determine certain parameters directly and
without estimation that the TCM 54 may otherwise need to estimate, and
vice versa. Also, the ECM 50 and the TCM 54 may be able to collect
information for certain parameters at a higher rate than can be
transmitted over the network 56. In other words, the frequency at which
the ECM 50 and the TCM 54 collect data may be higher than the frequency
at which the same data can be transferred over the network 56. The
bandwidth available for transfer of information between the ECM 50 and
the TCM 54 may be limited. For example, the ECM 50 may be able to collect
data from multiple engine speed sensors at a first rate, but may transfer
a single engine speed signal at a second rate over to the TCM 54. The
second rate may be less than the first rate. The sharing of information
allows the ECM 50 and TCM 54 to utilize information, otherwise estimated
or unavailable in performing engine and transmission control tasks.

[0029] The propulsion system 12 may also include auxiliary components,
such as an A/C compressor 60 and a steering pump 62. The MGU 18 and the
auxiliary components may be coupled to the ICE 16 using a belt and pulley
system 64. The belt and pulley system 64 may be coupled to a crankshaft
66 of the ICE 16 and enable torque to be transferred between the
crankshaft 66 and the MGU 18 and/or the auxiliary components. This
configuration is referred to as a belt alternator starter (BAS) system.
The crankshaft 66 drives the drivetrain system 14.

[0030] In operation, output torque from the MGU 18 may be applied to the
crankshaft 66. Propulsion torque of the crankshaft 66 is transferred
through the drivetrain system components to provide an axle torque
TAXLE at the axle shafts 38 to drive the wheels 42. The axle torque
TAXLE may be referred to as the powertrain output torque. More
specifically, the propulsion torque is multiplied by several gear ratios
provided by the coupling device 30, the transmission 32 and the
differential 36 to provide the axle torque TAXLE. Essentially, the
propulsion torque is multiplied by an effective gear ratio, which is a
function of a ratio introduced by the coupling device 30, a transmission
gear ratio determined by transmission input/output shaft speeds, a
differential ratio, as well as any other component that may introduce a
ratio in the drivetrain system 14 (e.g., a transfer case in a four wheel
drive (4WD) or all wheel drive (AWD) powertrain). For the purposes of
torque control, the axle torque domain includes the ICE 16 and the MGU
18.

[0031] The powertrain 10 also includes a control system 70, which may
regulate torque output of the engine 16 and the MGU 18. The control
system 70 includes the control modules 50, 52, 54. The control system 70
may regulate the torque output of the MGU 18 based on speed of the MGU
18, which may be detected by, for example, one or more engine speed
sensors 72. The engine speed sensors 72 may detect position and/or speed
of an object, such as position and/or speed of the crankshaft 66 (and/or
a camshaft). The information from the engine speed sensors 72 may be
provided directly to the control modules 50, 52, 54. In one embodiment,
the engine speed signals are provided to the ECM 50. The engine speed
signals may be considered raw engine speed signals until signal
conditioned by the ECM 50 or other signal conditioning circuitry.

[0032] The raw engine speed signals and/or the signal conditioned engine
speed signals may be generated based on notches, teeth, threads, mark,
etc. on, for example, a rotating object. The rotating object may be, for
example, the crankshaft 66, a camshaft, a flywheel, or a wheel, pulley or
gear connected to the crankshaft 66 or a camshaft. In one embodiment,
approximately 50-60 engine speed sensors 72 are used and positioned about
a circumference of a rotating object. This allows for precise position
and speed information on the rotating object. As an example, the ECM 50
may monitor rotation time between teeth of the rotating object, as
detected by the engine speed sensors 72. As another example, the ECM 50
may monitor rotation time of a tooth of the rotating object between
engine speed sensors 72. The ECM 50 may analyze the engine speed signals
and provide resulting information to the TCM 54. For example only, the
resulting information may include the mean and minimum engine speeds
SEmean, SEmin.

[0033] The mean engine speed SEmean may be generated based on one or
more firing events and/or one or more combustion cycles. A firing event
refers to a spark event of a cylinder of an engine. As an example, a four
cylinder four stroke engine may experience two firing events per
revolution of a crankshaft of the engine. Although the ECM 50 may receive
engine speed information from the engine speed signals for each firing
event and/or combustion cycle, the ECM 50 may not transmit all of this
information to the TCM 54.

[0034] The ECM 50 determines the mean and minimum engine speeds
SEmean, SEmin based on respective predetermined periods. The
predetermined periods may include multiple firing events and/or multiple
combustion cycles. The predetermined periods may be set to prevent a weak
cylinder from reducing engine speed to such an extent that a torque
converter lock-up occurs for more than a lock-up threshold period. By
providing the TCM 54 with mean and minimum engine speeds SEmean,
SEmin, the ECM 50 is informing the TCM 54 of the weak and/or weakest
cylinders. The TCM 54 is also informed of the strong and/or strongest
cylinders. The TCM 54 may then adjust torque slip accordingly.

[0035] The ECM 50 may monitor increases and decreases in the raw engine
speed (unconditioned or conditioned) SEraw and/or the mean engine
speed SEmean. For adequate isolation between the engine and
transmission sides of the torque converter 30 the ECM 50 may monitor the
mean engine speed SEmean, as opposed to the raw (or instantaneous)
engine speed SEraw. Minimum points in the raw engine speeds
SEraw and/or the mean engine speed SEmean may be detected
and/or averaged over a predetermined period. The ECM 50 may also, or as
an alternative, determine a difference between an engine speed (e.g., raw
engine speed SEraw and/or the mean engine speed SEmean) and a
minimum engine speed (e.g., the detected and/or average minimum engine
speeds) to generate an offset value. The ECM 50 may transmit the minimum
engine speeds, the average minimum engine speeds, and/or offset values to
the TCM 54. The engine speed and offset values may be transmitted
directly to the TCM 54 or to the memory 80 for access by the TCM 54.

[0036] The ECM 50, the HCM 52 and/or the TCM 54 control powertrain output
torque. The HCM 52 can include one or more sub-modules including, but not
limited to, a BAS control processor (BCP) 74. A driver input 76
communicates with the ECM 50. The driver input 76 can include, but is not
limited to, an accelerator pedal and/or a cruise control system input. A
driver interface 78 communicates with the TCM 54. The driver interface 78
includes, but is not limited to, a transmission range selector (e.g., a
PRNDL lever). The control modules 50, 52, 54 may communicate with memory
80, which includes tables 82. Information that is generated by each of
the modules 50, 52, 54 may be directly transmitted between the modules
50, 52, 54 or stored in the memory 80 for access by each of the modules.

[0037] Referring now also to FIG. 2, a functional block and schematic
diagram of a portion 100 of the hybrid powertrain system 10 is shown.
Portions of the propulsion, drivetrain and control systems 12, 14, 70 are
shown including the torque converter 30, the transmission 32, the ECM 50,
the TCM 54 and the crankshaft 66. The transmission 32 includes a
transmission gear and valve assembly 102 and a transmission pump 104.

[0038] The torque converter 30 includes an engine side 106, a transmission
side 108, and an electronically controlled capacity clutch (ECCC) 110.
The engine side 106 includes an impellar housing 112 (i.e. torque
converter pump) that is connected to the flexplate 27, which in turn is
connected to the crankshaft 66. The impellar housing 112 may be connected
to the transmission pump 104. The transmission side 108 includes a
turbine 114 that is connected to a transmission input shaft 116. The
transmission input shaft 116 is connected to the transmission gear and
valve assembly 102, which transfers torque to the driveshaft 34.

[0039] The propulsion torque from the crankshaft 66 is provided to the
flex plate 27 and in turn to the impellar housing 112. As the impellar
housing 112 is rotated, torque is transferred to the turbine 114, which
creates pump torque TP in the transmission pump 104. The
transmission pump 104 pumps transmission fluid to the transmission gear
and valve assembly 102 and to a lockup solenoid and valve assembly 120
via a transmission fluid path or line 122. Although, the transmission
fluid line 122 is shown as being connected between the transmission pump
104 and the lockup solenoid and valve assembly 120, the transmission
fluid line 122 also supplies fluid to the transmission gear and valve
assembly 102.

[0040] The TCM 54 controls pressure in the transmission fluid line 122 by
controlling apply and release fluid pressures PA and PR in the
torque converter 30, which in turn controls torque converter slip torque
Tslip between the impellar housing 112 and the turbine 114. The TCM
54 adjusts and maintains the torque converter slip torque Tslip, by
controlling pressure on the ECCC 110. The TCM 54 controls pressure on the
ECCC 110 by adjusting the fluid pressures PA and PR via the
lockup solenoid and valve assembly 120.

[0041] The TCM 54 communicates with the ECM 50 via the network 56. The ECM
50 receives engine speed signals from one or more engine speed sensors,
such as from an engine speed sensor 72'. The ECM 50 receives signals from
other sensors, such as from an engine coolant temperature (ECT) and
engine oil temperature (EOT) sensors 130, an oxygen sensor 132, a
throttle position sensor 134, an exhaust gas recirculation (EGR) sensor
136, intake sensors 138, exhaust sensors 140, an ambient air temperature
sensor 142, and a barometric pressure sensor 144. The intake sensors 138
may include a mass air flow (MAF) sensor, an intake air temperature (IAT)
sensor, and an intake manifold absolute pressure (MAP) sensor. The
exhaust sensors 136 may include exhaust flow, temperature and pressure
sensors.

[0042] The TCM 54 receives a turbine speed signal from a turbine speed
sensor 150. The TCM 54 may also receive sensor signals from sensors and
valves of the transmission and the lockup solenoid and valve assembly
120. For example, the TCM 54 may receive valve position signals, torque
converter pressure signals, transmission fluid pressure signals, etc.

[0043] The ECM 50 and the TCM 54 share various information over the
network 56. The ECM 50 may share, for example, engine speed information,
such as the mean and minimum engine speeds SEmean, SEmin with
the TCM 54. The ECM 50 may also share engine output torque and
acceleration information with the TCM 54. The TCM 54 controls operation
of the torque converter 30 and/or the transmission 32 based on the
information received from the ECM 50. The TCM 54 may share, for example,
propulsion torque (e.g., engine output torque), engine speed and engine
acceleration information with the ECM 50.

[0044] The ECM 50 may determine engine position, speed and/or minimum
engine speed based on: engine position and/or speed signals from the
engine speed sensors 72'; back torque information from the TCM 54; engine
speed information from the TCM 54; etc. The ECM 50 may determine
derivatives of engine position and engine speed to obtain acceleration
(and/or deceleration) of the engine 16. The position, speed (velocity)
and acceleration information may be determined based on: the engine speed
signals from the engine speed sensors; a propulsion torque signal, an
engine speed signal and/or an acceleration signal from the TCM 54; etc.

[0045] The ECM 50 may further monitor deviation in, for example, an
expected output torque of the engine 16 or deviation from a minimum spark
for best torque (MBT). The monitoring may be based on the engine speed,
engine acceleration, and propulsion torque signals from the TCM 54.
Determining, monitoring and receiving of engine speeds, engine
accelerations, and propulsion torques may be used to control operations,
such as throttle position, spark and fuel timing, and fuel quantities of
the engine 16.

[0046] The TCM 54 may determine derivatives of engine position and engine
speed to obtain acceleration (and/or deceleration) of the engine 16. The
position, speed (velocity) and acceleration information may be determined
based on: an engine speed signal from the ECM 50; engine speed signals
from engine speed sensors (e.g., the engine speed sensor 72'); the
turbine speed signal; pressures within the torque converter 30; etc.

[0047] Referring now also to FIG. 3, a functional block diagram of the ECM
50 and the TCM 54 is shown. The ECM 50 is distinct from and communicates
with the TCM 54 over the network 56. The ECM 50 includes a first
transceiver 160. The TCM 54 includes a second transceiver 162. In one
embodiment, the first and second transceivers 160, 162 are connected to
the network 56 via wired connections. In another embodiment, the first
transceiver 160 wirelessly communicates with the second transceiver 162.

[0048] The ECM 50 includes a first engine speed module 164, a minimum
engine speed module 165, an engine acceleration module 166, a spark
control module 168, a throttle control module 170, a fuel control module
172, a propulsion torque module 174, and may include other modules 178,
such as a cruise control module, a cylinder deactivation module, a
diagnostic module, etc. The modules 168, 170, 172, 174 may be referred to
as parameter control modules. The first engine speed module 164
determines the mean engine speed of the engine 16 based on engine speed
signals and/or other parameters described herein. The minimum engine
speed module 165 determines minimum engine speeds and/or average minimum
engine speeds over predetermined periods, as described herein.

[0049] The control modules 168, 170, 172, 174 control respectively spark
timing, throttle position, fuel timing and fuel quantities, and
propulsion torque or output torque of the engine 16 based on parameters
described with respect to the embodiments of FIGS. 1, 2 and 4. Example
parameters are engine speed, coolant and oil temperatures, barometric
pressures, etc.

[0050] The TCM 54 includes a turbine speed module 180, a second engine
speed module 182, an engine acceleration module 184, a hydrodynamic
torque module 186, a transmission pump torque module 188, a torque
converter module 190, a back torque module 192, a slip torque module 194,
and may include other modules 196. The other modules 196 may include a
lockup solenoid and valve assembly module 197 and a transmission gear and
valve assembly module 198. The turbine speed module 180 determines the
speed of the turbine 114 based on the turbine speed signals ST
and/or other parameters described herein. The module 186, 188, 190, 192
determine respectively hydrodynamic torques THYDINPUT,
THYDOUTPUT of the torque converter 30, transmission pump toque
TP of the transmission 32, torque converter clutch torque TCT,
and back torque TPROPTCM on the engine 16, as described with respect
to the embodiments of FIGS. 1, 2 and 4.

[0052] The lockup solenoid and valve assembly module 197 controls the
lockup solenoid and valve assembly 120, for example, to maintain the
predetermined clutch slip torque Tslip and/or to adjust the pressure
in the transmission fluid line 122. The transmission gear and valve
assembly module 198 may control the transmission gear and valve assembly
102 to adjust pressure in the transmission fluid line 122.

[0053] Referring now also to FIG. 4, a flow diagram illustrating a method
of operating a powertrain control system is shown. Although the following
tasks performed at 202-236 are described primarily with respect to the
embodiments of FIGS. 1-3, the tasks performed at 202-220 may be applied
to other embodiments of the present disclosure.

[0054] The method may begin at 200. At 202, engine speed sensors, such as
the sensors 72, 72', generate engine position and/or speed signals. At
204, the ECM 50 and/or the first engine speed module 164 generates a mean
engine speed signal SEmean based on the engine position and/or speed
signals. The mean engine speed signal SEmean may be an average
engine speed over a predetermined period and generated based on spark
timing, fuel quantities, misfire detection, etc. and transmitted to the
TCM 54. A misfire may refer to when fuel in a cylinder does not ignite
during a spark firing event. The predetermined period may be equal to
period of a combustion cycle of a cylinder or a full combustion cycle of
the engine 16.

[0056] At 207, the ECM 50 transmits the mean and minimum engine speed
information to the TCM 54. The mean and minimum engine speed information
may be nominally "smooth" (constant or with minimal fluctuations) and/or
free of cylinder-to-cylinder and/or other engine speed dynamics. At 208,
the turbine speed sensor 150 generates a turbine speed signal ST. In
one embodiment the TCM 54 proceeds from 207 to 209. In an alternative
embodiment, the TCM proceeds from 207 to 210.

[0057] At 209, the TCM 54 and/or the slip torque module 194 adjusts the
slip torque Tslip (targeted torque slip) based on the mean and
minimum engine speed information received as respective mean and minimum
engine speed signals. A desired slip torque may be determined using
equation 1. Although, torque slip of equation 1 is a function of mean
engine speed and minimum engine speed, torque slip may also be a function
of throttle position, spark timing, and fuel quantities. This additional
information may be provided from the ECM 50 to the TCM 54 or stored in
the memory 80.

Tslip=F{SEmean,SEmin} (1)

[0058] The minimum engine speed information may include the minimum engine
speed SEmin, an average minimum engine speed, or an offset value.
The torque slip Tslip may be a function of one or more of the
minimum engine speed, the average minimum engine speed, and the offset
value. Apply, release, and/or engage pressures PA, PR,
PTCC may be determined based on, for example, equations 2-3. The
fluid pressures PA and PR may be a function of, for example, a
commanded torque slip, a predetermined torque slip, the mean engine
speed, and/or the minimum engine speed or the offset value.

PA=F{Tslip,SEmean,SEmin} (2)

PR=F{Tslip,SEmean,SEmin} (3)

[0059] The engage pressure PTCC may be a commanded apply pressure
and/or based on the fluid pressures PA and PR and/or the fluid
pressure Pline in the transmission fluid line 122. As an example,
the engage pressure PTCC may be equal to a difference between the
fluid pressures PA and PR. The line pressure Pline may be
a commanded line pressure, an estimated line pressure, and/or directly
measured via a line pressure sensor. The line pressure Pline may be
determined based on the mean engine speed SEmean, a turbine speed
ST, the pressures PA and PR, etc.

[0060] For example, the torque slip Tslip may be increased when the
mean and/or minimum (or average minimum) engine speeds SEmean,
SEmin decrease to maintain at least a predetermined minimum torque
slip. Similarly, the torque slip Tslip may be decreased when the
mean and/or minimum (or average minimum) engine speeds SEmean,
SEmin increase to maintain at least the predetermined minimum torque
slip. As another example, the torque slip Tslip may be increased
when an offset value between an engine speed (raw or mean engine speed)
and the minimum (or average minimum) engine speed SEmin increases to
maintain at least the predetermined minimum torque slip and vice versa.

[0061] The predetermined minimum torque slip may be set to minimize engine
speed at idle for improved fuel economy while maintaining isolation
between the engine side and transmission side of the torque converter 30.
The predetermined minimum torque slip may be set, for example, by the TCM
54 to minimize the number of torque converter lock-ups and/or the period
in which the torque converter 30 is in a lock-up state. The TCM 54 may
monitor the number of lock-ups within a predetermined period and/or the
length of time that the TCM 54 remains in the lock-up state.

[0062] The torque slip Tslip, the apply, release and engage pressures
PA, PR, PTCC, and/or the line pressure Pline may be
adjusted based on the number of lock-ups within a predetermined period
and/or the length of time that the TCM 54 remains in the lock-up state.
The number of lock-ups and/or the length of time that the TCM 54 remains
in the lock-up state may be compared with respective thresholds. The
torque slip Tslip, the apply, release and engage pressures PA,
PR, PTCC, and/or the line pressure Pline may be adjusted
when one or more of the thresholds are exceeded.

[0064] The input and output hydrodynamic torques THYDINPUT,
THYDOUTPUT may be determined, for example, using equations 4-9. The
torque ratio (TR) is a function of the speed ratio (SR), as shown by
equation 5. The Cfactor and the Kfactor are based on the speed
ratio, as shown by equation 6. The Cfactor when plotted versus the
speed ratio SR is generally constant for values of the speed ratio SR
near 0. The Cfactor decreases at an increasing rate as the speed
ratio increases from 0 to 1.

[0067] At 216, the TCM 54 and/or back torque module 192 determines input
torque to, for example, the torque converter 30. The input torque is
equal to the back torque TPROPTCM applied on the crankshaft 66 by
the torque converter 30. The back torque TPROPTCM may be determined
using equations 12 or 13. The back torque TPROPTCM may be an average
or mean torque and may be equal to a sum of the torques acting on the
crankshaft 66 and downstream from the engine 16, such as a sum of the
input hydrodynamic torque THYDINPUT, the torque converter clutch
torque TCT, and the transmission pump torque T. The back torque
TPROPTCM may be used by an estimator of the TCM 54 and/or the ECM 50
for real-time (i.e., actual time at which an event occurs with negligible
delay) determination of engine speed, engine acceleration and combustion
torques.

TPROPTCM=F{THYDINPUT,TTC,TP} (12)

TPROPTCM=THYDINPUTTCT+TP (13)

[0068] At 218, the TCM 54 may receive, determine and/or monitor speed and
acceleration of the engine 16. The engine speed and/or acceleration may
be determined based on the input hydrodynamic torque THYDINPUT, the
torque converter clutch torque TCT and the transmission pump torque
TP. The torques THYDINPUT, TCT, TP may be commanded,
estimated and/or measured torque valves and are less susceptible to
measurement noise than differentiated engine speed signals. The TCM 54
may determine acceleration (and/or deceleration) of the engine 16 in
real-time and generate a first acceleration signal. The first
acceleration signal may be generated based on or as a function of the
propulsion torque TPROPTCM, the line pressure P line, the mean
engine speed SEmean (as determined by the ECM 50 and/or the TCM 54),
turbine speed ST, etc.

[0069] At 220, TCM 54 may adjust operation of the torque converter 30
and/or the transmission 32, such as by adjusting the slip torque
Tslip, the engage pressure PTCC, and/or the line pressure
Pline. The slip torque Tslip may be adjusted as described with
respect to the tasks at 209. After 209 and/or 220 control may return to
202 or end at 238, as shown.

[0070] The above-described tasks 202-220 are meant to be illustrative
examples; the tasks 202-220 may be performed sequentially, synchronously,
simultaneously, continuously, during overlapping time periods or in a
different order depending upon the application.

[0071] The real-time aspects of the above described embodiments allows for
improved torque converter and transmission performance and improved fuel
economy. Real-time information of engine speed information is fed forward
to estimators (e.g., respective modules of a TCM) of engine speed,
acceleration and combustion torque to account for dynamics in engine
speed and the effect of weak cylinders. A target slip torque is
determined based on the engine speed information to minimize torque
converter clutch lock-up events. Dynamics of an engine are determined
with reduced noise, as the dynamics are determined on engine side of a
torque converter, as opposed to on transmission side. Efficient minimum
slip clutch control is maintained while minimizing network bandwidth
usage.

[0072] The broad teachings of the disclosure can be implemented in a
variety of forms. Therefore, while this disclosure includes particular
examples, the true scope of the disclosure should not be so limited since
other modifications will become apparent to the skilled practitioner upon
a study of the drawings, the specification, and the following claims.